Inside the Longest Railway Tunnel
The Gotthard Base Tunnel drills 57 kilometres through the Swiss Alps — an engineering project that took nearly two decades to complete.
Opened in December 2016, the Gotthard Base Tunnel in Switzerland runs 57.1 kilometres beneath the Alps — the longest railway tunnel in the world. It connects Erstfeld in the north with Bodio in the south, shaving hours off freight routes between Rotterdam and Genoa while strengthening passenger links between German-speaking and Italian-speaking Switzerland.
The project concluded a vision first sketched in the 1940s: move rail traffic off steep mountain lines prone to winter closures and move it underground at nearly sea-level altitude through the continent's granite spine. Voters approved funding in multiple referendums, reflecting Swiss tolerance for long payback horizons when infrastructure quality is at stake.
Digging through granite
Two single-track tubes linked by cross-passages were bored through gneiss and sediment at depths reaching 2,300 metres below mountain peaks. Temperatures during excavation exceeded 40°C, requiring elaborate cooling systems and ventilation that could exchange air across the full length. Nine workers lost their lives over the project's seventeen-year construction — a sobering reminder of risks that persist even in nations famed for safety standards.
Tunnel boring machines longer than four football fields chewed through rock day and night. Disc cutters wore down under immense pressure and were replaced on schedules measured in hours of operation. Muck was transported back to the surface for use in landscaping and road projects, closing part of the material loop.
Precision beneath the mountains
Surveyors guided the north and south headings to meet within centimetres at breakthrough — a feat of geodesy involving laser gyroscopes and continuous correction for crustal movement. Waterproofing membranes and drainage galleries protect tracks from alpine groundwater that can reach pressures high enough to deform unfinished tubes.
Emergency stations every few kilometres provide refuge, ventilation reversals, and communication links monitored from control centres on both portals.
Gotthard taught a generation that patience with rock is not optional — the mountain sets the calendar, not the contractor. — tunnel engineering institute
Operations and freight
High-speed trains now pass at up to 250 km/h in a flat, straight alignment that replaces winding mountain lines. The tunnel is part of Switzerland's strategy to move heavy goods from road to rail, reducing alpine traffic and emissions. Freight trains up to 2,000 tonnes traverse the tubes nightly, carrying everything from automotive parts to containerised consumer goods.
Passenger services connect Zurich, Lugano, and Milan with schedules that compete with short-haul flights once airport security delays are counted.
Environmental and political context
Alpine ecosystems above the tunnel remain largely undisturbed compared with expanded surface corridors. Political debates preceded every bore metre, yet the finished project enjoys broad public pride as a symbol of Swiss competence.
Longer road tunnels exist, but for rail, Gotthard remained unmatched until companion projects such as the Brenner Base Tunnel advance on their own timelines.
Why it still matters
For civil engineers, Gotthard is a masterclass in boring machine logistics, cooling, and geotechnical unpredictability. For European trade, it is a artery that quietly moves GDP in the form of steel wheels on steel rails.
Travellers who pass through in twenty minutes may not see the two decades of labour behind the smooth ride — which is precisely the mark of infrastructure done well.